1. Field of the Invention
The present invention relates to the industry of instruments for measuring flow rates of fluids including petroleum products. The invention is more specifically directed to a method and an apparatus which carry out said method in order to measure the quantities of gas and liquid delivered in a gas-liquid mixture as it circulates within a duct without interrupting the flow.
One application for which the invention is particularly well-suited is operational control of oil wells under gas extraction and of wells which produce a mixture of gas and oil.
2. Description of the Prior Art
The methods and devices employed up to the present time or proposed for such measurements of flow rates have failed to give reliable industrial results and are usually very complex. Some systems involve the measurement of two different physical parameters such as velocity of sound and .gamma.-radiation whilst other systems of a more mechanical type have variable-pitch blades which are automatically adjustable as a function of the mean density of the fluid being transferred. Other devices for measuring multi-phase fluids have recourse to homogenization followed by sampling for analysis as described in U.K. Pat. No. 2,128,756.
Equipment units are also known for the purpose of separating gas and liquid in a mixture such as crude oil. The majority of these units involve settling in large tanks whilst other units make use of cyclones which are often mounted in series, as in Canadian Pat. No. 1,093,017, or in a complex structure as in Canadian Pat. No. 1,136,061. These large installations are neither suitable nor adaptable to sea-shore or offshore platform extractions and introduce considerable disturbances. In particular, they call for separate piping systems for conveying gas and liquid between the wellhead and the raw-product processing location.
The object of the invention is therefore to permit separate counting of gas and liquid in a more or less homogeneous gas-liquid mixture without interrupting the transfer of this latter, the apparatus employed for this purpose being simple, reliable and inexpensive to produce.